Magnetic tunnel junctions with control wire

ABSTRACT

A magnetic tunnel junction (MTJ) device is provided that includes a MTJ element and a control wire. The MTJ element includes a top ferromagnet layer formed of a first magnetic material, a tunneling layer, and a bottom ferromagnet layer formed of a second magnetic material. The tunneling layer is mounted between the top ferromagnet layer and the bottom ferromagnet layer. The control wire is configured to conduct a charge pulse. A direction of charge flow in the control wire extends substantially perpendicular to a magnetization direction of the top ferromagnet layer. The control wire is positioned sufficiently close to the top ferromagnet layer to reverse the magnetization direction of the top ferromagnet layer when the charge pulse flows therethrough while not reversing the magnetization direction of the bottom ferromagnet layer when the charge pulse flows therethrough.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application No. 61/884,262 that was filed Sep. 30, 2013, the entire contents of which is hereby incorporated by reference.

BACKGROUND

The application of spintronic technologies to general-purpose computing has been impeded by the difficulty in satisfying fundamental computing requirements. While the speed, power, and area of a logic gate are important, it is further important that the logical devices be connected in an efficient fashion such that the inputs and outputs of a logic gate are of such a form that the output of one gate can be used directly as the input of another gate without additional circuit elements; that is, the gates can be cascaded directly. Many proposed spintronic logic families do not permit direct cascading of logic gates, necessitating some combination of additional amplification, control logic, and logic execution stages. These processes require additional circuit elements such as complementary metal-oxide semiconductor transistors that consume significant power, processing time, and area, undermining the gains resulting from the use of spintronic technologies.

SUMMARY

In an illustrative embodiment, a magnetic tunnel junction device is provided. The magnetic tunnel junction device includes, but is not limited to, a MTJ element and a control wire. The MTJ element includes, but is not limited to, a top ferromagnet layer formed of a first magnetic material, a tunneling layer, and a bottom ferromagnet layer formed of a second magnetic material. The tunneling layer is mounted between the top ferromagnet layer and the bottom ferromagnet layer. The control wire is configured to conduct a charge pulse. A direction of charge flow in the control wire extends substantially perpendicular to a magnetization direction of the top ferromagnet layer. The control wire is positioned sufficiently close to the top ferromagnet layer to reverse the magnetization direction of the top ferromagnet layer when the charge pulse flows therethrough while not reversing the magnetization direction of the bottom ferromagnet layer when the charge pulse flows therethrough.

In another illustrative embodiment, magnetic tunnel junction device is provided. The magnetic tunnel junction device includes, but is not limited to, a first MTJ element, a second MTJ element, and a control wire. The first MTJ element includes, but is not limited to, a first top ferromagnet layer formed of a first magnetic material, a first tunneling layer, and a bottom ferromagnet layer formed of a second magnetic material. The first tunneling layer is mounted between the first top ferromagnet layer and the bottom ferromagnet layer. The second MTJ element includes, but is not limited to, a second top ferromagnet layer formed of the first magnetic material, a second tunneling layer, and the bottom ferromagnet layer. The second tunneling layer is mounted between the second top ferromagnet layer and the bottom ferromagnet layer. The control wire is configured to conduct a charge pulse. A direction of charge flow in the control wire extends substantially perpendicular to a magnetization direction of the first top ferromagnet layer and of the second top ferromagnet layer. The direction of charge flow in the control wire extends between the first top ferromagnet layer and the second top ferromagnet layer. The control wire is positioned sufficiently close to the first top ferromagnet layer and to the second top ferromagnet layer to reverse the magnetization direction of the first top ferromagnet layer and of the second top ferromagnet layer when the charge pulse flows therethrough while not reversing the magnetization direction of the bottom ferromagnet layer when the charge pulse flows therethrough.

Other principal features of the disclosed subject matter will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the disclosed subject matter will hereafter be described referring to the accompanying drawings, wherein like numerals denote like elements.

FIG. 1 depicts a schematic side view of a magnetic tunnel junction device in accordance with an illustrative embodiment.

FIG. 2 depicts a schematic perspective view of an inverter formed using the magnetic tunnel junction device of FIG. 1 in accordance with an illustrative embodiment.

FIG. 3 depicts a schematic perspective view of the inverter of FIG. 2 after a charge pulse flows through a control wire of the magnetic tunnel junction device in accordance with an illustrative embodiment.

FIG. 4 depicts a schematic perspective view of a ring oscillator formed using the magnetic tunnel junction device of FIG. 1 in accordance with an illustrative embodiment.

FIG. 5 depicts a schematic perspective view of an AND/OR/NAND/NOR gate formed using the magnetic tunnel junction device of FIG. 1 in accordance with an illustrative embodiment.

FIG. 6 depicts a schematic perspective view of a two-to-one multiplexer formed using the magnetic tunnel junction device of FIG. 1 in accordance with an illustrative embodiment.

FIG. 7 is a table showing a comparison between logic circuits implemented using a complementary metal-oxide semiconductor based structure and using the magnetic tunnel junction device of FIG. 1 in accordance with an illustrative embodiment.

DETAILED DESCRIPTION

With reference to FIG. 1, a schematic side view of a magnetic tunnel junction (MTJ) device 100 is shown in accordance with an illustrative embodiment. MTJ device 100 may include a MTJ element 102 and a control wire 104. MTJ element 102 may include a top ferromagnet layer 106, a tunneling layer 108, and a bottom ferromagnet layer 110. Tunneling layer 108 is mounted between top ferromagnet layer 106 and bottom ferromagnet layer 110.

As understood by a person of skill in the art, tunneling layer 108 forms an insulating layer that is thin enough (typically a few nanometers) to allow electrons to tunnel from top ferromagnet layer 106 to bottom ferromagnet layer 110 or vice versa. MTJ element 102 can be formed using a variety of thin film technologies as understood by a person of skill in the art.

Tunneling layer 108 acts as a tunnel barrier. A tunneling probability through tunneling layer 108 is determined by the orientation of the ferromagnet polarization of top ferromagnet layer 106 and bottom ferromagnet layer 110. When top ferromagnet layer 106 and bottom ferromagnet layer 110 have polarizations that are parallel and in the same direction, there is a higher probability of electron tunneling between top ferromagnet layer 106 and bottom ferromagnet layer 110 through tunneling layer 108. When top ferromagnet layer 106 and bottom ferromagnet layer 110 have polarizations that are parallel, but in opposite directions (anti-parallel), there is a lower probability of electron tunneling between top ferromagnet layer 106 and bottom ferromagnet layer 110 through tunneling layer 108. Large resistance ratios between the parallel and anti-parallel states are achievable. For example, magnetoresistance ratios greater than seven have been demonstrated at room temperature (See S. Ikeda, et al., “Tunnel magnetoresistance of 604% at 300 K by suppression of Ta diffusion in CoFeB/MgO/CoFeB pseudo-spin-valves annealed at high temperature,” Appl. Phys. Lett., vol. 93, pp. 082508, August 2008.). Higher ratios may be possible.

The magnetization direction of top ferromagnet layer 106 and bottom ferromagnet layer 110 can be switched with an external magnetic field. The required strength and duration of the magnetic field is determined by the material properties of top ferromagnet layer 106 and bottom ferromagnet layer 110. Top ferromagnet layer 106 is formed of a “soft” ferromagnetic material relative to the ferromagnetic material used to form bottom ferromagnet layer 110 such that a stronger magnetic field is applied to switch the magnetic polarization direction of bottom ferromagnet layer 110 than is applied to switch the magnetic polarization direction of top ferromagnet layer 106.

The magnetization of the “hard” magnetic material used to form bottom ferromagnet layer 110 is constant and in a −z direction as shown with reference to an x-z coordinate reference frame 112. The magnetization of the “soft” magnetic material used to form top ferromagnet layer 106 is selectable between a ±z direction based on application of a current through control wire 104. As a result, the respective magnetic materials used to form top ferromagnet layer 106 and bottom ferromagnet layer 110 are selected to achieve the relative difference in magnetic field that switches the magnetic polarization direction of top ferromagnet layer 106 without changing the magnetic polarization direction of bottom ferromagnet layer 110. Additionally, the relative dimensions between top ferromagnet layer 106 and bottom ferromagnet layer 110 may be selected to further achieve the relative difference in magnetic field applied to switch the magnetic polarization direction of top ferromagnet layer 106 without changing the magnetic polarization direction of bottom ferromagnet layer 110. Still further, the relative positioning between top ferromagnet layer 106 and bottom ferromagnet layer 110 may be selected to further achieve the relative difference in magnetic field applied to switch the magnetic polarization direction of top ferromagnet layer 106 without changing the magnetic polarization direction of bottom ferromagnet layer 110 by control wire 104. Merely for illustration, top ferromagnet layer 106, tunneling layer 108, and bottom ferromagnet layer 110 may be formed of CoFeB/MgO/CoFeB, respectively.

Control wire 104 is positioned adjacent to top ferromagnet layer 106 to extend in a ±x direction as shown with reference to x-z coordinate reference frame 112. Charge pulses flow through control wire 104 to create a magnetic field 120 that can switch the magnetization direction of top ferromagnet layer 106. If a charge pulse flows in the +x direction, the magnetization direction of top ferromagnet layer 106 is forced to the −z direction, parallel to the magnetization direction of bottom ferromagnet layer 110. MTJ element 102 enters its low resistance state because electrons can easily flow across tunneling layer 108. If a charge pulse flows through control wire 104 in the −x direction, the magnetization direction of top ferromagnet layer 106 is forced to the +z direction, anti-parallel to the magnetization direction of bottom ferromagnet layer 110. MTJ element 102 enters its high resistance state because electrons cannot easily flow across tunneling layer 108. The ferromagnetic materials used to form top ferromagnet layer 106 and bottom ferromagnet layer 110 may be selected to be non-volatile and to maintain the orientation of their magnetization when no external magnetic field is applied.

Control wire 104 may be formed of a variety of conductive materials and to have a variety of shapes and sizes that may be selected to induce a magnetic field when a charge pulse flows therethrough that is sufficient to switch the magnetization direction of top ferromagnet layer 106. Control wire 104 is further positioned sufficiently close to top ferromagnet layer 106 to switch the magnetization direction of top ferromagnet layer 106 when the charge pulse flows therethrough. Control wire 104 may be connected to a constant voltage node and a variable voltage node such that the charge pulse can be switched for transmission in the +x direction, the −x direction, or off.

With reference to FIG. 2, a schematic perspective view of an inverter device 200 is shown in accordance with an illustrative embodiment. Inverter device 200 may include a first MTJ element 102 a, a second MTJ element 102 b, and control wire 104. First MTJ element 102 a may include a first top ferromagnet layer 106 a, a first tunneling layer 108 a, and bottom ferromagnet layer 110. Second MTJ element 102 b may include a second top ferromagnet layer 106 b, a second tunneling layer 108 b, and bottom ferromagnet layer 110. First top ferromagnet layer 106 a and second top ferromagnet layer 106 b are similar to top ferromagnet layer 106 described with reference to MTJ element 102. First tunneling layer 108 a and second tunneling layer 108 b are similar to tunneling layer 108 described with reference to MTJ element 102. First tunneling layer 108 a is mounted between first top ferromagnet layer 106 a and bottom ferromagnet layer 110. Second tunneling layer 108 b is mounted between second top ferromagnet layer 106 b and bottom ferromagnet layer 110.

Inverter device 200 further may include a first electrode 202, a substrate 204, and a second electrode 206. First electrode 202 is formed on first top ferromagnet layer 106 a such that first top ferromagnet layer 106 a is positioned between first electrode 202 and first tunneling layer 108 a. First electrode 202 is formed of a conductive material such as a metal.

Bottom ferromagnet layer 110 is formed on substrate 204. Substrate 204 may be formed of a material such as silicon though other substrate materials may be used as understood by a person of skill in the art.

Second electrode 206 is formed on second top ferromagnet layer 106 b such that second top ferromagnet layer 106 b is positioned between second electrode 206 and second tunneling layer 108 b. Second electrode 206 is formed of a conductive material such as a metal.

Again, the magnetization of the “hard” magnetic material used to form bottom ferromagnet layer 110 is constant and in a −z direction as shown with reference to an x-y-z coordinate reference frame 208. The magnetization of the “soft” magnetic material used to form first top ferromagnet layer 106 a and second top ferromagnet layer 106 b is selectable between a ±z direction based on application of a current through control wire 104. Control wire 104 is positioned sufficiently close to first top ferromagnet layer 106 a and to second top ferromagnet layer 106 b to switch the magnetization direction of first top ferromagnet layer 106 a and/or second top ferromagnet layer 106 b when a charge pulse flows through control wire 104.

To act as an inverter, inverter device 200 outputs a signal opposite that of its input. In an initial state, first MTJ element 102 a is in its parallel state with first top ferromagnet layer 106 a switched to the −z direction. Second MTJ element 102 b is in its antiparallel state with second top ferromagnet layer 106 b switched to the +z direction. An output node connected to bottom ferromagnet layer 110 has an electric potential equal to a first electric potential applied to first electrode 202. When a charge pulse flows through control wire 104 in the +x direction, the magnetization of first top ferromagnet layer 106 a is switched to the +z direction and the magnetization of second top ferromagnet layer 106 b is switched to the −z direction, as shown in FIG. 3, causing the output node connected to bottom ferromagnet layer 110 to have an electric potential equal to a second electric potential applied to second electrode 206. In an illustrative embodiment, the second potential is less than the first potential causing electrons to flow through second MTJ element 102 b from second electrode 206 to bottom ferromagnet layer 110.

Direct cascading of logic gates can be achieved by using this electron current flow as an input charge pulse to other logic gates. By forming a capacitor with an insulating dielectric between bottom ferromagnet layer 110 and an input control wire, a charge pulse flows through the input control wire whenever the voltage on bottom ferromagnet layer 110 switches. The input control wire can be connected to drive other logic gates or as a logical output.

As an example, with reference to FIG. 4, a schematic perspective view of a ring oscillator device 400 is shown in accordance with an illustrative embodiment. ring oscillator device 400 may include a first inverter device 200 a, a second inverter device 200 b, a third inverter device 200 c, a first capacitor 402 a, a second capacitor 402 b, a third capacitor 402 c, and an reference conductor 408.

First inverter device 200 a is similar to inverter device 200 and may include a third top ferromagnet layer 106 aa, a third tunneling layer 108 aa, a fourth top ferromagnet layer 106 ba, a fourth tunneling layer 108 ba, a first bottom ferromagnet layer 110 a, a third electrode 202 a, a fourth electrode 206 a, and a first control wire 104 a. Second inverter device 200 b is similar to inverter device 200 and may include an fifth top ferromagnet layer 106 ab, a fifth tunneling layer 108 ab, a sixth top ferromagnet layer 106 bb, a sixth tunneling layer 108 bb, a second bottom ferromagnet layer 110 b, a fifth electrode 202 b, a sixth electrode 206 b, and a second control wire 104 b. Third inverter device 200 c is similar to inverter device 200 and may include an seventh top ferromagnet layer 106 ac, a seventh tunneling layer 108 ac, a eighth top ferromagnet layer 106 bc, a eighth tunneling layer 108 bc, a third bottom ferromagnet layer 110 c, a seventh electrode 202 c, an eighth electrode 206 c, and a third control wire 104 c. First bottom ferromagnet layer 110 a, second bottom ferromagnet layer 110 b, and third bottom ferromagnet layer 110 c are formed on substrate 204.

Third top ferromagnet layer 106 aa, fourth top ferromagnet layer 106 ba, fifth top ferromagnet layer 106 ab, sixth top ferromagnet layer 106 bb, seventh top ferromagnet layer 106 ac, and eighth top ferromagnet layer 106 bc are similar to top ferromagnet layer 106 described with reference to MTJ element 102. Third tunneling layer 108 aa, fourth tunneling layer 108 ba, fifth tunneling layer 108 ab, sixth tunneling layer 108 bb, seventh tunneling layer 108 ac, and eighth tunneling layer 108 bc are similar to tunneling layer 108 described with reference to MTJ element 102. First bottom ferromagnet layer 110 a, second bottom ferromagnet layer 110 b, and third bottom ferromagnet layer 110 c are similar to bottom ferromagnet layer 110 described with reference to MTJ element 102.

Third tunneling layer 108 aa is formed between third top ferromagnet layer 106 aa and first bottom ferromagnet layer 110 a. Fourth tunneling layer 108 ba is formed between fourth top ferromagnet layer 106 ba and first bottom ferromagnet layer 110 a. Fifth tunneling layer 108 ab is formed between fifth top ferromagnet layer 106 ab and second bottom ferromagnet layer 110 b. Sixth tunneling layer 108 bb is formed between sixth top ferromagnet layer 106 bb and second bottom ferromagnet layer 110 b. Seventh tunneling layer 108 ac is formed between seventh top ferromagnet layer 106 ac and third bottom ferromagnet layer 110 c. Eighth tunneling layer 108 bc is formed between eighth top ferromagnet layer 106 bc and third bottom ferromagnet layer 110 c.

Third electrode 202 a, fourth electrode 206 a, fifth electrode 202 b, sixth electrode 206 b, seventh electrode 202 c, and eighth electrode 206 c are formed of a conductive material such as a metal. Third electrode 202 a, fifth electrode 202 b, and seventh electrode 202 c are similar to first electrode 202 and mounted on third top ferromagnet layer 106 aa, fifth top ferromagnet layer 106 ab, and seventh top ferromagnet layer 106 ac, respectively. Fourth electrode 206 a, sixth electrode 206 b, and eighth electrode 206 c are similar to second electrode 206 and mounted on fourth top ferromagnet layer 106 ba, sixth top ferromagnet layer 106 bb, and eighth top ferromagnet layer 106 bc, respectively. The first electric potential is applied to third electrode 202 a, fifth electrode 202 b, and seventh electrode 202 c. The second electric potential is applied to fourth electrode 206 a, sixth electrode 206 b, and eighth electrode 206 c.

First capacitor 402 a may include a first conductive layer 404 a and a first dielectric layer 406 a. First dielectric layer 406 a is formed of a dielectric material mounted on first bottom ferromagnet layer 110 a. First conductive layer 404 a is mounted on first dielectric layer 406 a such that first dielectric layer 406 a is mounted between first conductive layer 404 a and first bottom ferromagnet layer 110 a.

Second capacitor 402 b may include a second conductive layer 404 b and a second dielectric layer 406 b. Second dielectric layer 406 b is formed of a dielectric material mounted on second bottom ferromagnet layer 110 b. Second conductive layer 404 b is mounted on second dielectric layer 406 b such that second dielectric layer 406 b is mounted between second conductive layer 404 b and second bottom ferromagnet layer 110 b.

Third capacitor 402 c may include a third conductive layer 404 c and a third dielectric layer 406 c. Third dielectric layer 406 c is formed of a dielectric material mounted on third bottom ferromagnet layer 110 c. Third conductive layer 404 c is mounted on third dielectric layer 406 c such that third dielectric layer 406 c is mounted between third conductive layer 404 a and third bottom ferromagnet layer 110 c.

First control wire 104 a is connected between first conductive layer 404 a and reference conductor 408. Second control wire 104 b is connected between second conductive layer 404 b and reference conductor 408. Third control wire 104 c is connected between third conductive layer 404 c and reference conductor 408. A third electric potential is applied to reference conductor 408. For illustration, the first electric potential>the third electric potential>the second electric potential. However, there are no constraints on the relationships between the first electric potential, the third electric potential, and the second electric potential because the electric potentials can be selected to achieve a specific circuit behavior as understood by a person of skill in the art.

Again, the magnetization of the “hard” magnetic material used to form first bottom ferromagnet layer 110 a, second bottom ferromagnet layer 110 b, and third bottom ferromagnet layer 110 c is constant and in a −z direction.

The magnetization of the “soft” magnetic material used to form third top ferromagnet layer 106 aa and fourth top ferromagnet layer 106 ba is selectable between a ±z direction based on application of a current through third control wire 104 c. Third control wire 104 c is positioned sufficiently close to third top ferromagnet layer 106 aa and to fourth top ferromagnet layer 106 ba to switch the magnetization direction of third top ferromagnet layer 106 aa and of fourth top ferromagnet layer 106 ba when a charge pulse flows through third control wire 104 c.

The magnetization of the “soft” magnetic material used to form fifth top ferromagnet layer 106 ab and sixth top ferromagnet layer 106 bb is selectable between a ±z direction based on application of a current through first control wire 104 a. First control wire 104 a is positioned sufficiently close to fifth top ferromagnet layer 106 ab and to sixth top ferromagnet layer 106 bb to switch the magnetization direction of fifth top ferromagnet layer 106 ab and of sixth top ferromagnet layer 106 bb when a charge pulse flows through first control wire 104 a.

The magnetization of the “soft” magnetic material used to form seventh top ferromagnet layer 106 ac and eighth top ferromagnet layer 106 bc is selectable between a ±z direction based on application of a current through second control wire 104 b. Second control wire 104 b is positioned sufficiently close to seventh top ferromagnet layer 106 ac and to eighth top ferromagnet layer 106 bc to switch the magnetization direction of seventh top ferromagnet layer 106 ac and of eighth top ferromagnet layer 106 bc when a charge pulse flows through second control wire 104 b.

Whenever the voltage on first conductive layer 404 a switches, a charge pulse flows through first control wire 104 a. The charge pulse flowing through first control wire 104 a results in switching of the magnetization of fifth top ferromagnet layer 106 ab and sixth top ferromagnet layer 106 bb, causing the voltage on second conductive layer 404 b to switch. When the voltage on second conductive layer 404 b switches, a charge pulse flows through second control wire 104 b. The charge pulse flowing through second control wire 104 b results in switching of the magnetization of seventh top ferromagnet layer 106 ac and eighth top ferromagnet layer 106 bc, causing the voltage on third conductive layer 404 c to switch. When the voltage on third conductive layer 404 c switches, a charge pulse flows through third control wire 104 c. The charge pulse flowing through third control wire 104 c results in switching of the magnetization of third top ferromagnet layer 106 aa and fourth top ferromagnet layer 106 ba, causing the voltage on first conductive layer 404 a to switch. As a result, the signal propagates through ring oscillator device 400. This direct cascading scheme provides complementary inputs and outputs because the current can be routed across each inverter device 200 a, 200 b, 200 c in either direction.

As another example, with reference to FIG. 5, a schematic perspective view of a logic gate 500 is shown in accordance with an illustrative embodiment. Logic gate 500 can be configured to perform logical AND, OR, NAND, NOR, etc. operations. Logic gate 500 may include a third MTJ element 102 d, a fourth MTJ element 102 e, a fifth MTJ element 102 f, a sixth MTJ element 102 g, a seventh electrode 202 d, an eighth electrode 202 e, a ninth electrode 202 f, a tenth electrode 202 g, a fourth capacitor 402 d, substrate 204, a second reference conductor 502, and a third reference conductor 504. For illustration, third MTJ element 102 d, fourth MTJ element 102 e, fifth MTJ element 102 f, and sixth MTJ element 102 g are shown offset in the y-direction though this arrangement is merely for visual clarity.

Third MTJ element 102 d may include a ninth top ferromagnet layer 106 d, a ninth tunneling layer 108 d, and a fourth bottom ferromagnet layer 110 d. Seventh electrode 202 d is similar to first electrode 202 and is mounted on ninth top ferromagnet layer 106 d.

Fourth MTJ element 102 e may include a tenth top ferromagnet layer 106 e, a tenth tunneling layer 108 e, and fourth bottom ferromagnet layer 110 d. Eighth electrode 202 e is similar to first electrode 202 and is mounted on tenth top ferromagnet layer 106 e.

Fifth MTJ element 102 f may include a eleventh top ferromagnet layer 106 f, a eleventh tunneling layer 108 f, and fourth bottom ferromagnet layer 110 d. Ninth electrode 202 d is similar to first electrode 202 and is mounted on eleventh top ferromagnet layer 106 f.

Sixth MTJ element 102 g may include an twelfth top ferromagnet layer 106 g, a twelfth tunneling layer 108 g, and a fifth bottom ferromagnet layer 110 e. Tenth electrode 202 g is similar to first electrode 202 and is mounted on twelfth top ferromagnet layer 106 g. Fourth bottom ferromagnet layer 110 d and fifth bottom ferromagnet layer 110 e are formed on substrate 204.

Ninth top ferromagnet layer 106 d, tenth top ferromagnet layer 106 e, eleventh top ferromagnet layer 106 f, and twelfth top ferromagnet layer 106 g are similar to top ferromagnet layer 106 described with reference to MTJ element 102. Ninth tunneling layer 108 d, tenth tunneling layer 108 e, eleventh tunneling layer 108 f, and twelfth tunneling layer 108 g are similar to tunneling layer 108 described with reference to MTJ element 102. Ninth tunneling layer 108 d is formed between ninth top ferromagnet layer 106 d and fourth bottom ferromagnet layer 110 d. Tenth tunneling layer 108 e is formed between tenth top ferromagnet layer 106 e and fourth bottom ferromagnet layer 110 d. Eleventh tunneling layer 108 f is formed between eleventh top ferromagnet layer 106 f and fourth bottom ferromagnet layer 110 d. Twelfth tunneling layer 108 g is formed between twelfth top ferromagnet layer 106 g and fifth bottom ferromagnet layer 110 e.

Fourth capacitor 402 d may include a fourth conductive layer 404 d and a fourth dielectric layer 406 d. Fourth dielectric layer 406 d is formed of a dielectric material mounted on fourth bottom ferromagnet layer 110 d. Fourth conductive layer 404 d is mounted on fourth dielectric layer 406 d such that fourth dielectric layer 406 d is mounted between fourth conductive layer 404 d and fourth bottom ferromagnet layer 110 d.

A fourth control wire 104 d is connected between a first input (not shown) and second reference conductor 502. A fifth control wire 104 e is connected between a second input (not shown) and second reference conductor 502. A sixth control wire 104 f is connected between ninth electrode 202 f and tenth electrode 202 g. A seventh control wire 104 g is mounted between fourth conductive layer 404 d and an output (not shown). The first electric potential, V⁺, is applied to seventh electrode 202 d and eighth electrode 202 e. The third electric potential, V_(c), is applied to second reference conductor 502. The second electric potential, V⁻, is applied to third reference conductor 504.

Again, the magnetization of the “hard” magnetic material used to form fourth bottom ferromagnet layer 110 d and fifth bottom ferromagnet layer 110 e is constant and in a −z direction.

The magnetization of the “soft” magnetic material used to form ninth top ferromagnet layer 106 d and eleventh top ferromagnet layer 106 f is selectable between a ±z direction based on application of a current through fourth control wire 104 d. Fourth control wire 104 d is positioned sufficiently close to ninth top ferromagnet layer 106 d and to eleventh top ferromagnet layer 106 f to switch the magnetization direction of ninth top ferromagnet layer 106 d and of eleventh top ferromagnet layer 106 f when a charge pulse flows through fourth control wire 104 d.

The magnetization of the “soft” magnetic material used to form tenth top ferromagnet layer 106 e and twelfth top ferromagnet layer 106 g is selectable between a ±z direction based on application of a current through fifth control wire 104 e. Fifth control wire 104 e is positioned sufficiently close to tenth top ferromagnet layer 106 e and to twelfth top ferromagnet layer 106 g to switch the magnetization direction of tenth top ferromagnet layer 106 e and of twelfth top ferromagnet layer 106 g when a charge pulse flows through fifth control wire 104 e.

Logic gate 500 can be configured to perform logical AND, OR, NAND, and/or NOR operations. For example, to perform logical a logical AND operation, an input current applied through fourth control wire 104 d in the +y direction and through fifth control wire 104 e in the −y direction and an output current received through seventh control wire 104 g in the +y direction can be considered a logical “1”. Table I below shows the input current state on fourth control wire 104 d and fifth control wire 104 e, the state of each of third MTJ element 102 d, fourth MTJ element 102 e, fifth MTJ element 102 f, and sixth MTJ element 102 g, and the output voltage and current state on seventh control wire 104 g. An “On” state indicates the respective ferromagnet layers are in parallel orientation, and an “Off” state indicates the respective ferromagnet layers are in antiparallel orientation.

TABLE I 104d 104e 102d 102f 102g 102e V 104g I 104g 0 0 On Off Off On V⁺ 0 0 1 On Off On Off V⁺ 0 1 0 Off On Off On V⁺ 0 1 1 Off On On Off V⁻ 1

To perform a logical OR operation, an input current applied through fourth control wire 104 d in the −y direction and through fifth control wire 104 e in the +y direction and an output current received through seventh control wire 104 g in the −y direction can be considered a logical “1”. Table II below shows the input current state on fourth control wire 104 d and fifth control wire 104 e, the state of each of third MTJ element 102 d, fourth MTJ element 102 e, fifth MTJ element 102 f, and sixth MTJ element 102 g, and the output voltage and current state on seventh control wire 104 g.

TABLE II 104d 104e 102d 102f 102g 102e V 104g I 104g 0 0 Off On On Off V⁻ 0 0 1 Off On Off On V⁺ 1 1 0 On Off On Off V⁺ 1 1 1 On Of Off On V⁺ 1

To perform a logical NOR operation, an input current applied through fourth control wire 104 d in the −y direction and through fifth control wire 104 e in the +y direction and an output current received through seventh control wire 104 g in the +y direction can be considered a logical “1”. Table II below shows the input current state on fourth control wire 104 d and fifth control wire 104 e, the state of each of third MTJ element 102 d, fourth MTJ element 102 e, fifth MTJ element 102 f, and sixth MTJ element 102 g, and the output voltage and current state on seventh control wire 104 g.

TABLE III 104d 104e 102d 102f 102g 102e V 104g I 104g 0 0 Off On On Off V⁻ 1 0 1 Off On Off On V⁺ 0 1 0 On Off On Off V⁺ 0 1 1 On Of Off On V⁺ 0

To perform a logical NAND operation, an input current applied through fourth control wire 104 d in the −y direction and through fifth control wire 104 e in the +y direction and an output current received through seventh control wire 104 g in the +y direction can be considered a logical “1”. Table II below shows the input current state on fourth control wire 104 d and fifth control wire 104 e, the state of each of third MTJ element 102 d, fourth MTJ element 102 e, fifth MTJ element 102 f, and sixth MTJ element 102 g, and the output voltage and current state on seventh control wire 104 g.

TABLE IV 104d 104e 102d 102f 102g 102e V 104g I 104g 0 0 On Off Off On V⁺ 0 0 1 On Off On Off V⁺ 0 1 0 Off On Off On V⁺ 0 1 1 Off On On Off V⁻ 1

Logic gate 500 can be configured to perform any two-input AND or OR function with any combination of polarities through appropriate interpretation of the current direction for the inputs and the output.

As another example, with reference to FIG. 6, a schematic perspective view of a multiplexer 600 is shown in accordance with an illustrative embodiment. Multiplexer 600 may include a seventh MTJ element 102 h, an eighth MTJ element 102 i, a ninth MTJ element 102 j, a tenth MTJ element 102 k, an eleventh MTJ element 102 l, a twelfth MTJ element 102 m, an eleventh electrode 202 h, a twelfth electrode 202 i, a thirteenth electrode 206 d, a fourteenth electrode 206 e, a fifth capacitor 402 e, substrate 204, a fourth reference conductor 602, and a conductor 604. For illustration, seventh MTJ element 102 h, eighth MTJ element 102 i, ninth MTJ element 102 j, tenth MTJ element 102 k, eleventh MTJ element 102 l, and twelfth MTJ element 102 m are shown offset in the x-direction though this arrangement is merely for visual clarity.

Seventh MTJ element 102 h may include a thirteenth top ferromagnet layer 106 h, a thirteenth tunneling layer 108 h, and a sixth bottom ferromagnet layer 110 f. Eleventh electrode 202 h is similar to first electrode 202 and is mounted on thirteenth top ferromagnet layer 106 h. The first electric potential, V⁺, is applied to eleventh electrode 202 h.

Eighth MTJ element 102 i may include a fourteenth top ferromagnet layer 106 i, a fourteenth tunneling layer 108 h, and a seventh bottom ferromagnet layer 110 g. Twelfth electrode 202 i is similar to first electrode 202 and is mounted on fourteenth top ferromagnet layer 106 i. The first electric potential, V⁺, is applied to twelfth electrode 202 i.

Ninth MTJ element 102 j may include a fifteenth top ferromagnet layer 106 j, a fifteenth tunneling layer 108 j, and sixth bottom ferromagnet layer 110 f. Thirteenth electrode 206 d is similar to second electrode 206 and is mounted on fifteenth top ferromagnet layer 106 j. The second electric potential, V⁻, is applied to thirteenth electrode 206 d.

Tenth MTJ element 102 k may include a sixteenth top ferromagnet layer 106 k, a sixteenth tunneling layer 108 k, and seventh bottom ferromagnet layer 110 g. Fourteenth electrode 206 e is similar to second electrode 206 and is mounted on sixteenth top ferromagnet layer 106 k. The second electric potential, V⁻, is applied to fourteenth electrode 206 e.

Eleventh MTJ element 102 l may include a seventeenth top ferromagnet layer 106 l, a seventeenth tunneling layer 108 l, and sixth bottom ferromagnet layer 110 f. Conductor 604 is mounted on seventeenth top ferromagnet layer 106 l.

Twelfth MTJ element 102 m may include a eighteenth top ferromagnet layer 106 m, a eighteenth tunneling layer 108 m, and seventh bottom ferromagnet layer 110 g. Conductor 604 is mounted on eighteenth top ferromagnet layer 106 m.

Fifth capacitor 402 e may include a fifth conductive layer 404 e and a fifth dielectric layer 406 e. Fifth dielectric layer 406 e is formed of a dielectric material mounted on conductor 604. Fifth conductive layer 404 e is mounted on fifth dielectric layer 406 e such that fifth dielectric layer 406 e is mounted between fifth conductive layer 404 e and conductor 604.

An eighth control wire 104 h is connected between a first input (not shown) and fourth reference conductor 602. A ninth control wire 104 i is connected between a second input (not shown) and fourth reference conductor 602. A tenth control wire 104 j is connected between a third input (not shown) and fourth reference conductor 602. An eleventh control wire 104 k is mounted between fifth conductive layer 404 e and an output (not shown). The third electric potential, V_(c), is applied to fourth reference conductor 602.

Again, the magnetization of the “hard” magnetic material used to form sixth bottom ferromagnet layer 110 f and seventh bottom ferromagnet layer 110 g is constant and in a −z direction.

The magnetization of the “soft” magnetic material used to form thirteenth top ferromagnet layer 106 h and fifteenth top ferromagnet layer 106 j is selectable between a ±z direction based on application of a current through eighth control wire 104 h. Eighth control wire 104 h is positioned sufficiently close to thirteenth top ferromagnet layer 106 h and to fifteenth top ferromagnet layer 106 j to switch the magnetization direction of thirteenth top ferromagnet layer 106 h and of fifteenth top ferromagnet layer 106 j when a charge pulse flows through eighth control wire 104 h.

The magnetization of the “soft” magnetic material used to form fourteenth top ferromagnet layer 106 i and sixteenth top ferromagnet layer 106 k is selectable between a ±z direction based on application of a current through ninth control wire 104 i. Ninth control wire 104 i is positioned sufficiently close to fourteenth top ferromagnet layer 106 i and to sixteenth top ferromagnet layer 106 k to switch the magnetization direction of fourteenth top ferromagnet layer 106 i and of sixteenth top ferromagnet layer 106 k when a charge pulse flows through ninth control wire 104 i.

The magnetization of the “soft” magnetic material used to form seventeenth top ferromagnet layer 106 l and eighteenth top ferromagnet layer 106 m is selectable between a ±z direction based on application of a current through tenth control wire 104 j. Tenth control wire 104 j is positioned sufficiently close to seventeenth top ferromagnet layer 106 l and to eighteenth top ferromagnet layer 106 m to switch the magnetization direction of seventeenth top ferromagnet layer 106 l and of eighteenth top ferromagnet layer 106 m when a charge pulse flows through tenth control wire 104 j.

Multiplexer 600 can be configured to perform a two-to-one multiplexing operation. An input current applied through eighth control wire 104 h, ninth control wire 104 i, and tenth control wire 104 j in the +x direction and an output current received through eleventh control wire 104 k in the +x direction can be considered a logical “1”. Table V below shows the input current state on eighth control wire 104 h, ninth control wire 104 i, and tenth control wire 104 j, the state of each of MTJ element 102 h, 102 i, 102 j, 102 k, 102 l, 102 l, and the output voltage and current state on eleventh control wire 104 k. An “on” state indicates the respective ferromagnet layers are in parallel orientation, and an “off” state indicates the respective ferromagnet layers are in antiparallel orientation.

TABLE V 104j 104h 104i 102l 102m 102h 102j 102i 102k V 104k I 104k 0 0 0 on off off on off on V⁻ 0 0 0 1 on off off on on off V⁻ 0 0 1 0 on off on off off on V⁺ 1 0 1 1 on off on off on off V⁺ 1 1 0 0 off on off on off on V⁻ 0 1 0 1 off on off on on off V⁺ 1 1 1 0 off on on off off on V⁻ 0 1 1 1 off on on off on off V⁺ 1

A doubling in logical efficiency is achieved using multiplexer 600 as compared to fully complementary CMOS. Coupled with the increased switching efficiency available with spintronic techniques, the logical efficiency of multiplexer 600 provides improved power, performance, and area.

Any logic function can be performed using one or more MTJ device 100 with an equal number or fewer devices and stages than with CMOS. The increased logical efficiency using one or more MTJ device 100 as compared to fully complementary CMOS can be seen in FIG. 7. This new logic family has significant implications on the circuit design process. In terms of physical layout, logic gate 500 allows for increased reliance on standard cells. Additionally, the flexibility in cascading polarization opens up new opportunities and challenges for wire routing.

As used in this disclosure, the term “mount” includes join, unite, connect, couple, associate, insert, hang, hold, affix, attach, fasten, bind, paste, secure, bolt, screw, rivet, pin, nail, clasp, clamp, cement, fuse, solder, weld, glue, form over, form on, slide together, layer, deposit, sputter, and other like terms. The phrases “mounted on” and “mounted to” include any interior or exterior portion of the element referenced. These phrases also encompass direct mounting (in which the referenced elements are in direct contact) and indirect mounting (in which the referenced elements are not in direct contact, but are mounted together via intermediate elements). Elements referenced as mounted to each other herein may further be integrally formed together, for example, using a molding process as understood by a person of skill in the art. As a result, elements described herein as being mounted to each other need not be discrete structural elements. The elements may be mounted permanently, removably, or releasably.

The use of directional terms, such as top, bottom, right, left, front, back, up, down, etc. are merely intended to facilitate reference to the various surfaces of the described structures relative to the orientations shown in the drawings and are not intended to be limiting. The use of the terms “first”, “second”, “third”, etc. are merely used to distinguish one element from another and are not intended to be limiting.

The dimensions provided herein are illustrative as one skilled in the art could deviate from these dimensions and obtain similar results. The word “illustrative” is used herein to mean serving as an illustrative, instance, or illustration. Any aspect or design described herein as “illustrative” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, “a” or “an” means “one or more”. Still further, using “and” or “or” in the detailed description is intended to include “and/or” unless specifically indicated otherwise. The illustrative embodiments may be implemented as a method, apparatus, or article of manufacture

It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. The foregoing description of illustrative embodiments of the disclosed subject matter has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the disclosed subject matter to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed subject matter. The embodiments were chosen and described in order to explain the principles of the disclosed subject matter and as practical applications of the disclosed subject matter to enable one skilled in the art to utilize the disclosed subject matter in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the disclosed subject matter be defined by the claims appended hereto and their equivalents. 

What is claimed is:
 1. A magnetic tunnel junction device comprising: a magnetic tunnel junction (MTJ) element comprising a top ferromagnet layer formed of a first magnetic material; a tunneling layer; and a bottom ferromagnet layer formed of a second magnetic material, wherein the tunneling layer is mounted between the top ferromagnet layer and the bottom ferromagnet layer; and a control wire configured to conduct a charge pulse, wherein a direction of charge flow in the control wire extends substantially perpendicular to a magnetization direction of the top ferromagnet layer, wherein the control wire is positioned sufficiently close to the top ferromagnet layer to reverse the magnetization direction of the top ferromagnet layer when the charge pulse flows therethrough while not reversing the magnetization direction of the bottom ferromagnet layer when the charge pulse flows therethrough.
 2. The magnetic tunnel junction device of claim 1, wherein the first magnetic material and the second magnetic material are the same material.
 3. The magnetic tunnel junction device of claim 1, wherein the first magnetic material and the second magnetic material are different materials selected such that the control wire positioned sufficiently close to the top ferromagnet layer reverses the magnetization direction of the top ferromagnet layer when the charge pulse flows therethrough.
 4. The magnetic tunnel junction device of claim 1, wherein the direction of charge flow can be reversed.
 5. The magnetic tunnel junction device of claim 4, wherein, when the direction of charge flow is reversed, the magnetization direction of the top ferromagnet layer is reversed.
 6. The magnetic tunnel junction device of claim 5, wherein, when the direction of charge flow is reversed, a magnetization direction of the bottom ferromagnet layer is not reversed.
 7. A magnetic tunnel junction device comprising: a first magnetic tunnel junction (MTJ) element comprising a first top ferromagnet layer formed of a first magnetic material; a first tunneling layer; and a bottom ferromagnet layer formed of a second magnetic material, wherein the first tunneling layer is mounted between the first top ferromagnet layer and the bottom ferromagnet layer; a second MTJ element comprising; a second top ferromagnet layer formed of a third magnetic material; a second tunneling layer; and the bottom ferromagnet layer, wherein the second tunneling layer is mounted between the second top ferromagnet layer and the bottom ferromagnet layer; and a control wire configured to conduct a charge pulse, wherein a direction of charge flow in the control wire extends substantially perpendicular to a magnetization direction of the first top ferromagnet layer and of the second top ferromagnet layer, wherein the direction of charge flow in the control wire extends between the first top ferromagnet layer and the second top ferromagnet layer, wherein the control wire is positioned sufficiently close to the first top ferromagnet layer and to the second top ferromagnet layer to reverse the magnetization direction of the first top ferromagnet layer and of the second top ferromagnet layer when the charge pulse flows therethrough while not reversing the magnetization direction of the bottom ferromagnet layer when the charge pulse flows therethrough.
 8. The magnetic tunnel junction device of claim 7, further comprising: a dielectric layer mounted on the bottom ferromagnet layer; a conducting layer mounted on the dielectric layer opposite the bottom ferromagnet layer; and a second control wire electrically coupled to the conducting layer and configured to conduct a second charge pulse.
 9. The magnetic tunnel junction device of claim 8, further comprising: a third MTJ element comprising a third top ferromagnet layer formed of a fourth magnetic material; a third tunneling layer; and a second bottom ferromagnet layer formed of a fifth magnetic material, wherein the third tunneling layer is mounted between the third top ferromagnet layer and the second bottom ferromagnet layer; and a fourth MTJ element comprising; a fourth top ferromagnet layer formed of a sixth magnetic material; a fourth tunneling layer; and the second bottom ferromagnet layer, wherein the fourth tunneling layer is mounted between the fourth top ferromagnet layer and the second bottom ferromagnet layer; wherein a direction of charge flow in the second control wire extends substantially perpendicular to a magnetization direction of the third top ferromagnet layer and of the fourth top ferromagnet layer, wherein the direction of charge flow in the second control wire extends between the third top ferromagnet layer and the fourth top ferromagnet layer, wherein the second control wire is positioned sufficiently close to the third top ferromagnet layer and to the fourth top ferromagnet layer to reverse the magnetization direction of the third top ferromagnet layer and of the fourth top ferromagnet layer when the second charge pulse flows therethrough while not reversing the magnetization direction of the second bottom ferromagnet layer when the charge pulse flows therethrough.
 10. The magnetic tunnel junction device of claim 9, further comprising: a second dielectric layer mounted on the second bottom ferromagnet layer; and a second conducting layer mounted on the second dielectric layer opposite the second bottom ferromagnet layer; wherein the control wire is electrically coupled to the second conducting layer.
 11. The magnetic tunnel junction device of claim 8, further comprising: a third MTJ element comprising a third top ferromagnet layer formed of a fourth magnetic material; a third tunneling layer; and the bottom ferromagnet layer, wherein the third tunneling layer is mounted between the third top ferromagnet layer and the bottom ferromagnet layer; a fourth MTJ element comprising; a fourth top ferromagnet layer formed of a fifth magnetic material; a fourth tunneling layer; and a second bottom ferromagnet layer, wherein the fourth tunneling layer is mounted between the fourth top ferromagnet layer and the second bottom ferromagnet layer; and a third control wire configured to conduct a third charge pulse, wherein a direction of charge flow in the third control wire extends substantially perpendicular to a magnetization direction of the third top ferromagnet layer and of the fourth top ferromagnet layer, wherein the direction of charge flow in the third control wire extends between the third top ferromagnet layer and the fourth top ferromagnet layer, wherein the third control wire is positioned sufficiently close to the third top ferromagnet layer and to the fourth top ferromagnet layer to reverse the magnetization direction of the third top ferromagnet layer and of the fourth top ferromagnet layer when the third charge pulse flows therethrough while not reversing the magnetization direction of the bottom ferromagnet layer or of the second bottom ferromagnet layer when the third charge pulse flows therethrough.
 12. The magnetic tunnel junction device of claim 11, wherein the charge pulse defines a first logical input signal and the third charge pulse defines a second logical input signal.
 13. The magnetic tunnel junction device of claim 12, wherein the second charge pulse defines a logical output signal determined based on the first logical input signal and the second logical input signal.
 14. The magnetic tunnel junction device of claim 7, wherein the first magnetic material and the third magnetic material are the same material.
 15. The magnetic tunnel junction device of claim 7, further comprising: a first reference conductor mounted on a side of the first top ferromagnet layer opposite the first tunneling layer; and a second reference conductor mounted on a side of the second top ferromagnet layer opposite the second tunneling layer; wherein a first electric potential applied to the first reference conductor is greater than a second electric potential applied to the second reference conductor when the first electric potential is applied to the first reference conductor and the second electric potential is applied to the second reference conductor. 